1. Field
This disclosure relates generally to charging a device and, more specifically to techniques for charging a wireless device.
2. Related Art
Today, wire-free power solutions for mobile devices are becoming more common. For example, WildCharge, Inc. of Boulder, Colo. offers wire-free power products that include a WildCharger™ pad and WildCharger™ adapter. The WildCharger™ pad is a charging pad that can be produced using a variety of rigid or flexible materials. The charging pad has no buttons or controls and can be configured to provide power to charge and operate one or more devices (e.g., laptop computer systems, personal digital assistants (PDAs), and mobile phones) simultaneously. To facilitate device charging via a charging pad, a WildCharger™ adapter may be attached to or integrated in an electronic device.
When a charging pad enabled electronic device, such as a mobile phone, is placed on the charging pad, electrical contacts on the adapter of the device electrically contact parallel conductors formed on a surface of the charging pad. Power is then conductively transferred from the pad to the device via two of the parallel conductors and two of the electrical contacts. In general, the geometries of the electrical contacts are designed such that irrespective of the position of the device with respect to the surface of the pad, a closed electrical circuit is formed between two of the parallel conductors and two of the contacts of the device to facilitate powering and charging of the device. In a typical embodiment, one or more permanent magnets may be implemented within a device to improve conductivity between the parallel conductors and the contacts.
In contrast to a permanent magnet, an electromagnet is a type of magnet in which a magnetic field is produced in response to electric current flow. In an electromagnet, a magnetic field disappears when electric current flow through a coil of the electromagnet ceases. For example, a simple electromagnet may be produced by passing an electric current through a wire (to generate a magnetic field around the wire). In general, a magnetic field strength generated is proportional to an amount of current that passes through a wire. In order to concentrate a magnetic field generated by a wire, the wire may be wound into a coil, which includes multiple turns of wire side-by-side. In the case of a coil, a magnetic field provided by all turns of the wire pass through a center of the coil. In general, stronger magnetic fields can be produced if a core of ferromagnetic material (e.g., soft iron) is placed inside the coil. In this case, the core essentially magnifies the magnetic field. Electromagnets have been used in a wide variety of electric devices, e.g., motors and generators, relays, bells, loudspeakers, and magnetic locks.